This invention relates to a polycyanoaryl ether and a method of preparing the same. More specifically, this invention relates to a polycyanoaryl ether which is excellent in heat resistance and which has good fire retardance, solvent resistance and mechanical strength, and a method of preparing the same. Further, this invention relates to a method of preparing a polycyanoaryl ether in which high molecular weight polymer is easily obtained and productivity is high. Furthermore, it relates to a method of preparing a sufficiently purified fine polycyanoaryl ether powder without requiring any process of grinding the prepared polymer.
As materials for electrical and electronic equipments and mechanical parts, polycyanoaryl ethers have been known.
In Japanese Unexamined Patent Publications Nos. 14270/1972 and 206433/1984, polycyanoaryl ethers having various structures are disclosed. These polymers have excellent mechanical properties and are useful as industrial materials, but their heat resistance is not considered to be satisfactory.
These polycyanoaryl ethers may be prepared as undermentioned. For example, in Japanese Unexamined Patent Publication No. 14270/1972, a method is disclosed in which dinitrobenzonitrile is reacted with a divalent phenol to prepare the polycyanoaryl ether. However, the polycyanoaryl ether prepared by such a method is poor in heat resistance as mentioned above, and does not have a sufficiently high molecular weight.
In addition thereto, this polymer is relatively coarse, and thus a mechanical grinding is necessary to pulverize it into a sufficiently fine state for a purification step. In this grinding process, a great deal of energy is consumed, and since the grain diameter of the thus ground powder is relatively large, it is difficult to obtain a satisfactory purification effect.